The present invention relates to an abnormality detection method and system which detect abnormality by checking sleep mode operations of electronic control units for electronically controlled devices.
Recent automotive vehicles use a multiplex communication system to reduce wire harnesses that connect electronic control units (ECUs) one another. In the multiplex communication system, a network is formed by connecting the ECUs as nodes via a common multiplex communication line so that the ECUs execute data communication through the multiplex communication line. The ECUs for similar controls are preferably grouped to form a plurality of networks for improving data communication in the vehicle. In this case a data relay device is provided to enable data communication among the ECUs in different networks. One of the ECUs is used as an abnormality monitoring unit that collects information of abnormality occurring in the ECUs or ECU-controlled devices based on data frames transmitted from the ECUs.
JP-A-11-341572 proposes one abnormality detection system that circulates a check memory in a network. The check memory has the same number of data bits as that of ECUs of the network. Each ECU sets a flag in a bit allocated therefor when the check memory is circulated thereto, and transmits the check memory to another ECU of the next address. If the ECU receives no confirmation frame from the ECU of next address, the ECU transmits the check memory to the ECU of the further next address. Thus, this abnormality detection system specifies an ECU having an abnormality based on the flag of the check memory after the check memory is circulated once.
JP-A-11-332086 proposes another abnormality detection system in which a power supply line is arranged in parallel with a multiplex communication line that connects ECUs. The communication line is influenced by an abnormality in the power supply line, resulting in abnormality in the communication line. Thus this abnormality detection system detects the abnormality in the power supply by monitoring the number of abnormalities in the communication line.
These proposed systems are however incapable of detecting abnormalities of ECU-controlled devices as long as the ECUs for the vehicle devices operate normally to transmit the data frames.